The present invention relates to a drive system for a motor vehicle. More specifically, the present invention relates to an electric motor drive unit for use in hybrid electric motor vehicles.
To reduce the volume of pollutants exhausted into the air by automotive powertrains driven exclusively by an internal combustion engine, hybrid powertrains that include an electric motor and an IC engine, which operate independently or and in combination, have been developed.
Hybrid electric powertrains are being developed for use in four-wheel drive vehicles such that the motor and the engine can transmit power to both a front set of driven wheels and rear set of driven wheels. Hybrid four-wheel drive systems, however, present packaging difficulties to the vehicle designer. When packaging an electric motor drive unit for a front axle or rear axle it is preferable to place the motor drive unit on the axle centerline for best packaging efficiency.
Packaging an electric motor on an axle and eliminating the need for a 90-degree bevel gear differential provides an electric hybrid powertrain with a substantial improvement in packaging efficiency. Performance improvement and better fuel economy accompany the packaging efficiency.
A need exists for hybrid electric powertrains applicable to four-wheel drive vehicles that use conventional powertrain components, minimize package space, and reduce manufacturing and assembly costs.